Provably Fair Provably Fair
A method that lets players verify for themselves, using cryptographic hashes, that a game result was not tampered with after the bet was placed. It is mainly used in crypto casino games such as Crash and Dice.
| English | Provably Fair |
|---|---|
| Classification | Math & Probability |
| English | Provably Fair |
| Category | Math & Probability |
| Core technology | SHA-256 hash, HMAC |
| Components | Server seed, client seed, nonce |
| Games that commonly use it | Crash, Dice, Plinko, Roulette, Blackjack |
| Limits | Does not guarantee licensing, RTP or withdrawals |
| Compared with | RNG certification (independent testing labs) |
Overview
Provably Fair is a method that uses cryptography to let players check for themselves that “the result of this round was not changed after the bet was placed.” It’s mainly used in games like Crash, Dice, and Plinko at crypto casinos.
How it works
| Step | Details |
|---|---|
| 1. Before betting | The game side creates a secret “server seed,” converts it into a SHA-256 hash (a 64-character fingerprint), and publishes it in advance. The seed itself stays hidden. |
| 2. While betting | The server seed is combined with the player’s “client seed” and a number that changes with each bet, the “nonce,” and an HMAC calculation produces the result. |
| 3. After betting | When the game side reveals the original server seed, the player calculates the hash themselves and checks that it matches the fingerprint published at the start. |
If the two hashes match, it means the game side used the same server seed from the start and didn’t change it midway. Changing even a single character of the input produces a completely different result, so any tampering would be exposed right away.
Games where it’s mainly used
| Games | What the seeds determine |
|---|---|
| Crash | The point where the multiplier stops |
| Dice | The number that comes up |
| Plinko | The path the ball falls along |
| Roulette | Result pocket (0-36) |
| Blackjack | Card order |
Some games mix the crash format into slots, like Nolimit City’s xCrash, but standard slots usually get RNG certification from independent testing labs instead of Provably Fair.
Limitations
- Proves only the integrity of a single round: It only proves that the result of that round came out according to a predetermined calculation, and it doesn’t prove the trustworthiness of the operator itself.
- The house edge stays: Verifying doesn’t remove the house edge or improve the odds. RTP is still determined by the game’s design.
- Separate from licensing: Operators that aren’t regulated can also offer Provably Fair games. It doesn’t guarantee withdrawals or player protection.
- No outside oversight: Unlike RNG certification verified by independent testing labs, Provably Fair relies on the player’s own verification.